Answer:
RC = 40
Explanation:
Note that the circumcentre is equally distant from the triangle's 3 vertices.
That is : PC = RC = QC
Equate any pair and solve for x
Using RC = PC, then
5x - 15 = 3x + 7 ( subtract 3x from both sides )
2x - 15 = 7 ( add 15 to both sides )
2x = 22 ( divide both sides by 2 )
x = 11
Hence
RC = (5 × 11) - 15 = 55 - 15 = 40 units